Pollution linked with birth defects in U.S. study

They said their study, published in the American Journal of Epidemiology, is the first definitively to link air pollution with birth defects.

"There seems to be something in the air that can harm developing fetuses," Beate Ritz, an epidemiologist who headed the study, said in a statement.

The team, at the University of California Los Angeles (UCLA) School of Public Health and the California Birth Defects Monitoring Program, said the two pollutants they measured were carbon monoxide and ozone - produced by the city's well-known traffic jams.

"The greater a woman's exposure to one of these two pollutants in the critical second month of pregnancy, the greater the chance that her child would have one of these serious cardiac birth defects," Ritz said.

"More research needs to be done, but these results present the first compelling evidence that air pollution may play a role in causing some birth defects."

Ritz's team compared air pollution monitoring data from the Environmental Protection Agency with information from the California Birth Defects Monitoring Program - a statewide database on birth defects.

They looked at 9,000 babies born from 1987 to 1993. Pregnant women who were exposed to the highest levels of ozone and carbon monoxide because their homes were close to busy freeways were three times as likely to have a child with certain heart defects as women breathing the cleanest air.

The defects they found were specific - conotruncal heart defects, pulmonary artery/valve defects and aortic artery/valve defects, which can require open-heart surgery to save the baby. No other birth defects were linked with the pollution.

SOMETHING ELSE COULD BE THE CULPRIT

The researchers said it was not certain carbon monoxide and ozone were directly causing the defects. They could be a "marker" - something associated with the real cause.

"We're not sure carbon monoxide is the culprit because it could be just a marker for something else in tailpipe exhaust," Gary Shaw of the California Birth Defects Monitoring Program said in a statement.

"The fact that certain heart defects are turning up in the second month of pregnancy when hearts are being formed suggests something serious may be happening."

Ritz said fine particles may be to blame."We did a small study that showed ultrafine particles correlate extremely well with carbon monoxide," she said in a telephone interview.

"When you move away from a freeway, 100 feet, 200 feet, you see the number of particles decrease very steeply. So does carbon monoxide."

She said other researchers had shown that these ultrafine particles, which also come out of the tailpipes of cars, can carry toxic chemicals such as quinones and polycyclic aromatic hydrocarbons (PAHs). "They become a great delivery device for toxic agents," Ritz said.

The same goes for ozone, which is generated when the sun cooks polluted air. The same process generates other chemicals, which are not measured.

"It's easy as a knee-jerk reaction to say 'Let's get ozone down, let's get carbon monoxide down.' But if you are not doing anything to the other toxins, you might be on the wrong boat," Ritz said.

Ritz said it also occurred to her that people living near freeways may also be poorer or have worse health in general, but said she factored that in. Some of the affected neighborhoods were actually very wealthy, she said.

She also looked at ethnicity and education level of the mothers and found no differences in the correlation between pollution and birth defects.

But she said they were unable to evaluate other potential risk factors for birth defects, including smoking, occupational exposures, vitamin supplement use, diet and obesity.